The invention pertains to an intraocular hydrogel lens with shape memory swelling in water or isotonic solution, as is physiological saline, which is deformed before implantation to the shape suitable for operative introduction, for example to the shape of a rod, and is designated for insertion inside an eye into the anterior or posterior chamber or behind the cornea.
The intraocular lenses known so far are predominantly in a definite shape and physical state before their operative insertion into the eye. Such lenses are made either from hard polymers, as are polymers of esters of methacrylic acid or acrylic acid with lower aliphatic alcohols, for example, from methyl methacrylate (MMA), or from soft hydrogels swollen to equilibrium in physiological saline before insertion into the eye. A relatively long incision is needed in both cases in order to slide the lens into its place. The hard lenses cannot be deformed at applicable temperature to facilitate the insertion. With common hydrogel lenses from lightly crosslinked polymers, as is the polymer of hydroxyethyl methacrylate (HEMA), the possible temporary deformation is limited, if not excluded, by their elasticity and tendency to break at too sharp bending. Moreover, the hard lenses increase the risk of injury of sensitive eye tissues during insertion.
Recently an intraocular lens is known which is deformed before and during operation to a shape suitable for operative insertion, thus enabling one to shorten the incision (U.S. Pat. No. 4,731,079; Czechoslovak Patent Application No. 9596-86). The lens acquires its final shape first in the eye on the place designated for it.
The purposeful deformation is, for example, winding or compression of the lens to a narrow rod or, at least, its folding or coiling in order to reduce the necessary length of incision at least in half.
After operative insertion, which is considerably facilitated by this deformation, the lens relaxes in the eye under heating to eye temperature and thus acquires the desirable original shape, elasticity, and softness. The rate of unfolding is given beforehand and the surgeon has to work very quickly and with handiness without making a mistake.
According to the references mentioned above, the lens is either not swollen to equilibrium and undergoes postswelling in eye (Czechoslovak Patent Application No. 9596-86) or is swollen to equilibrium with a low content of water (up to 20%) and the water content does not change in eye (U.S. Pat. No. 4,731,079).